adapt train example to use classes

Train/Track.svg

@@ -7,6 +7,20 @@
    version="1.1"
    id="svg5154">
 
+    <style id="style_ttd_ts_mp">
+        .ttd {
+            stroke : none;
+            stroke-width: 0.2;
+            opacity: 0.7
+        }
+        .red-occupied-ttd {
+            fill : red
+        }
+        .blue-cleared-ttd {
+            fill : blue
+        }
+   </style>
+   
   <polygon id = "train_polygon"
        points="0,0 100,0"
        style="stroke-width: 0.3"
@@ -32,15 +46,11 @@
        transform="translate(10,23)" />
   <polygon id = "occupied_ttd_polygon"
        points="0,0 0,2 10,2 10,0 70,0 70,1 90,1 90,0"
-       stroke="none" fill="red"
-       opacity="0.70"
-       style="stroke-width: 0.2"
+       class = "ttd red-occupied-ttd"
        transform="translate(10,23)" />
   <polygon id = "cleared_ttd_polygon"
        points="0,0 10,2 20,2 20,0 90,0 90,1 100,1 100,0"
-       stroke="none" fill="blue"
-       opacity="0.70"
-       style="stroke-width: 0.2"
+       class = "ttd blue-cleared-ttd"
        transform="translate(10,23)" />
 
     <text  text-align="left"  x="5"  y="41"